Dry rectifier



Dec. 18, 1934. w. c. VAN GEEL ETAL DRY RECTIFIER Filed Jan. 22, 1951 azat Ifendr v'k [men a, J

Patented 18, 1934 UNITED STATES PATENT OFFICE Application January 22, 1831, Serial No. 510,580 In the Netherlands March 8, 1930 1 claim. (01. HR)

'Ihe invention relates to dry rectifiers. Such a rectifier commonly comprises two plates, preferably of conducting material, which are placed the one on the other and between which is provided an intermediate layer of a third material.

According to the invention, the cathode of the rectifier consists, at least in part, of a metal of the first sub-group of the fourth principal group of the periodic system.

It has been found that with these metals (titanium, zirconium, hafnium and thorium) a highly satisfactory rectifying effect can be obtained.

The cathode consisting of one of these metals is preferably coated with a layer consisting of one or more compounds of this metal. Use is preferably made of a film consisting of one or more oxides of the metal constituting the cathode.

It has been found that owing to the extreme permanency of the oxides of these metals the rectifiers thus produced have an almost unlimited life.

For the anode of said rectifiers, in which the cathode consists of a metal of the first sub-group of the fourth principal group, use should preferably be made. of a compound containing as negative constituent one of the elements of the halogen group, the oxygen group or the nitrogen group or of a mixture of such compounds. For this purpose these substances while being in a powdery state, may be compressed to form plates.

' It is often advantageous to add to the material of the anode a certain quantity of one or more of the free elements of the said groups.

Very favorable results have been obtained with an anode consisting of cuprous sulfide to which may be added free sulphur, and with an anode of copper iodide which may have added to it free iodine. An anode consisting of phosphorhas also proved to give excellent results.

The metal compounds may be formed from the material of the electrode itself. This may be efifected either electrolytically or chemically.

On heating, for example, a zirconium plate in an atmosphere of nitrogen to a temperature of I analogous manner.

For obtaining a surface layer on titanium, thorium or hafnium one may proceed in an For obtaining a superficial layer by electrolysis, one may utilize, for example for the oxidation ofzirconium, the electrolytes phosphoric acid, sulfuric acid, lye or ammoniumborate. As the one electrode a zirconium plate is-placed'in the bath whereas for the other electrode use may be made of a rod of platinum. carbon or of an- 10 other material which cannot be attacked. The thickness of the layer may be concluded upon by the colour which the plate assumes during oxidation. With zirconium a satisfactory thickness of the oxide layer is obtained, for example, '15 by electrolytically oxidizing until the surface of the zirconium plate has taken a yellowish green colour.

With the metals titanium and hafnium one may proceed in a similar manner. For thorium, 20 however, this method has proved to be less suitable so that in this case use should preferably be made of chemical means.

As above noted, it is advantageous to utilize for the anode cuprous sulfide to which may be 25 added some free sulphur. If, for example, the cells are built up from a zirconium plate coated with an oxide layer and a cuprous sulfide plate one obtains a rectifier which has a very satisfactory characteristic and which appears to be 30 almost independent from temperature influences.

Of other materials which also give satisfactory results when they are used as anode with a cathode of a metal of the first sub-group of the 'fourth principal group, copper iodide to which 35 may be added some free iodine, has already been mentioned.

Lead sulfide, molybdenum sulfide, tungsten sulfide, iron sulfide, iron hammer scale may also enter into consideration, more particularly if it 40 is desired to obtain a rectifier with a slight internal resistance. In order to obtain a higher internal resistance, use may be made of an anode of manganese oxide, silver chloride with free iodine, lead dioxide and cadmium oxide. The anode material may consequently be chosen in accordance with the tensions to be applied and with the current intensity to be obtained.

The accompanying drawing represents schematically a dry rectifier adapted to rectify a twophase alternating current and composed of some of the above described rectifier cells.

The plates a which are coated with an oxide layer 1) consist, for example, of zirconium and constitute the cathodes. The plates c consist for 56 example or pressed we, iodide with'treeiodine. Owing to the fact that at the points where .an

oxide layer is present the current passes only in the direction from c to a, it will be evident that in the circuit-arrangement shown full-wave rectification oi the alternating current is obtained, with which during each half-cycle in series are traversed. c The above-described rectifiers may be utilized for all purposes for which rectifiers have been utilized up to the present. In view oi the manner-in which the rectifier is to be utilized, it is possible to choose a suitable combination for the.

material of the electrodes. a Thus, for example a rectifier destined for a low tension and a large current intensity and whose cells consist of the combination oi zirconium provided with an oxide layer and cuprous film and the anode of a mixture of silver chlo-' sulfide, will be particularly suitable for charging.

ride and free iod ne. Such rectifiers maybe employed, for example, in plate-tension supply units.

What we claim is:

1. A dry rectifier having a cathode and an anode, said cathode being formed substantially of one of the metals of the first sub-group of the fourth principal group oifthe periodic system, and a layer of oxide 0! the cathode metal coating said cathode, the anode comprising a metal compound which contains as its negative component one of theelements of the oxygen-group.

4o 2. Adry rectifier having a cathode and an anode, said cathode being formed substantially of one of the metals or the first sub-group of the fourth principal group of the periodic system, and a layer of oxide of the cathode metal 4,5 coating said cathode, the anode comprising a means metal compound which contains as its negative two'elements I component one'oi. the elements oi the oxygengroup to which. has been added acertain qu'an-- tity of at least one of the free elements of the oxygen-group.

8. A dry rectifier having a cathode and an anode, said cathode being formed substantially of one of the metals of the first sub-group oi the. fourth principal group oi. the periodic system, a layer of oxide of the cathode metal coat-.

ing said cathode, the anode comprising cuprous sulfide.

4. A dry rectifier having a cathode and an anode, said cathode being formed substantially ,or vone oi the meta'lsoi the first sub-group of the tourth principal group oi the periodic system, a layer of oxide of the cathode metal coating said cathode, the anode comprising cuprous sulfide to Y which tree sulphur has been added.

5. A dry rectifier having a cathode and-an anode, said cathode being formed substantiallyof one of the metals of the first sub-group oi the fourthprincipal group of the periodic system, a layer-oi oxide oi' the cathode metal ooat-' ing said cathode, the ahodecomprising a compound which contains as its negative component at least one of the elements selected from the group comprising the halogen-group, the oxygengroup, and the nitrogen-group.

6. A dry rectifier having a cathode and an anode, said cathode being iormedsubstantially of one of the metals of the first sub-group of the fourth principal group of the periodic system, said anode comprising copper iodide. f

'I. A dry rectifier having a cathode and an anode, said cathode being formed substantially of one oi! the metals 0! the first sub-group of the fourth principal group of the periodic system,

said anode comprising copper iodideto which iree iodine has been added.

WILLEM CHRIBTIAAN VAR GEEL. JAN HENDRIX DI BOER. HENDRIX EMMENB. 

